Seeking Advice on Replacing HH O-Rings in the Truck

[Welder1]

Pull the mushroom air intake cap and have someone standby with a board to block the air intake in case of a run away condition. If the shutoff lever has an issue it could take the engine to full throttle.

 

[GunInstructordotcom]

Pull the mushroom air intake cap and have someone standby with a board to block the air intake in case of a run away condition. If the shutoff lever has an issue it could take the engine to full throttle.

That makes sense. When I get it buttoned back up I will do that, just to be safe, before i start it. Thank you for the tip.

 

[M37M35]

That makes sense. When I get it buttoned back up I will do that, just to be safe, before i start it. Thank you for the tip.

Also, look on the back side of the air filter housing toward the engine. There's probably a 1" port there that might have to be plugged, or else the board over the intake won't completely kill the engine.

 

[GunInstructordotcom]

Also, look on the back side of the air filter housing toward the engine. There's probably a 1" port there that might have to be plugged, or else the board over the intake won't completely kill the engine.

It started up after a bit of cranking and letting the tank pump fill the low pressure lines. Runs a bit rough, but idles. Forgot to tighten down injector line #5, spitted a bit of diesel. Then while it warmed up, I noticed it was leaking from the base of the HH. This was where it was leaking before I replaced the o-rings.

I should mention that, when I first removed the injector lines, two of the HH ports had rusty sludge in them. They happened to be the two lines that had cracked rubber water covers. When I cleaned out those ports in the HH with q-tips, there was much red rust sludge in the bottom of those two ports. The fittings on the two lines were also rusty between the hex head and the threads. I'm wondering if the HH is malfunctioning. Perhaps the two lines are clogged? Could that explain the leak at the base, the weak, rough acceleration and the smoky exhaust?

 

[M37M35]

Perhaps the two lines are clogged?

With the rubber covers bad, I'm not surprised there was crud in the threads. I doubt the lines or ports are clogged, but it's easy enough to find out. You can loosen the lines one at a time at the injector and start the engine and see if they spray diesel.

 

[GunInstructordotcom]

With the rubber covers bad, I'm not surprised there was crud in the threads. I doubt the lines or ports are clogged, but it's easy enough to find out. You can loosen the lines one at a time at the injector and start the engine and see if they spray diesel.

The rust muck was all the way down in the hole in the HH that the line screws into. Tomorrow morning I will try to verify where the leak is coming from while it is running. Is leaking diesel from the HH base a possible symptom of a cracked HH?

 

[M37M35]

I haven't had to do any major work on my HH, so I don't know enough about the inner workings to be much help in that area. Hopefully someone with more experience with the HH will chime in on that.

A couple years ago I did the same thing you just did and replaced my HH O-rings because I was getting diesel in the oil. The process went okay and the engine ran fine afterwards. I haven't had to mess with the IP or HH other than that.

...weak, rough acceleration and the smoky exhaust?

Did the engine run good before you worked on the HH?

 

[smoke]

If the mating surface between the line and the head has any defect or crap there, you are going to have a leak. Considering the pressure, the slightest defect and the fuel will push by or through it. Also When you started it back up you could of push the sludge through the line up to injector. Maybe its time to pull injectors and check pop-off pressure, spray pattern and clean the tips. When you had it apart did you spray anything or blow air through all the injector lines to check they were clean and clear before reinstalling? If you can post some pics of the area that would help.

 

[smoke]

Forgot to add any of this problems and you could be running on less cylinders or not properly firing ones. Weak, rough acceleration, etc....

 

[Elk1111]

I’m not sure if it’s the best idea or not but on mine I ended up putting orings in each injection line connection to fix the same problem your having. My hydraulic head was old and pitted and that’s the only way I could keep it from leaking.

 

[GunInstructordotcom]

I haven't had to do any major work on my HH, so I don't know enough about the inner workings to be much help in that area. Hopefully someone with more experience with the HH will chime in on that.

A couple years ago I did the same thing you just did and replaced my HH O-rings because I was getting diesel in the oil. The process went okay and the engine ran fine afterwards. I haven't had to mess with the IP or HH other than that.


Did the engine run good before you worked on the HH?

Yes, it ran more smoothly. It did smoke until it warmed up. Later today when there is shade, I'm going to try to determine where the diesel leak is coming from. I will shield the area from the fan so I can see better where the tiny stream is coming from. The fan blows it onto the steering shaft.

 

[GunInstructordotcom]

It occurred to me that I have not replaced the primary and secondary fuel filters in many years. So I'm going to tackle that task before I start it up again and try to determine where the leak is coming from near the HH. I noticed in the military manual that there is a bleeding process for the filters that includes loosening the injector lines at the injectors until no more air escapes. I didn't do that after replacing the HH o-rings. I hope I didn't screw something up by not bleeding them.

 

[GunInstructordotcom]

I have never changed out the fuel filters. In the past, a mechanic did it for me. The military manual states that the first step is to drain the filter through the petcock. I did so, but shut it off after much more came out than what I believe the filter can hold. Does the draining also empty the fuel lines back to the tank and forward to the secondary filters? Or am I missing a detail such as a shutoff valve for the fuel line?

 

[M37M35]

I hope I didn't screw something up by not bleeding them.

No, you didn't hurt anything.

Does the draining also empty the fuel lines back to the tank and forward to the secondary filters? Or am I missing a detail such as a shutoff valve for the fuel line?

There's no shutoff valve.

If you're draining the primary filter on the frame rail first, there's a chance it could siphon fuel from the tank.
I don't remember the exact procedure in the manual, but I think if you drained the two filters on the block first, left the drain valves open so it can draw air, then drained the primary, it wouldn't be able to siphon from the tank.
If you collect the drained fuel into clean containers, you can let it set for awhile so any water and junk settles to the bottom, then pour the clean fuel off the top back into the tank so not much is wasted.

 

[GunInstructordotcom]

No, you didn't hurt anything.


There's no shutoff valve.

If you're draining the primary filter on the frame rail first, there's a chance it could siphon fuel from the tank.
I don't remember the exact procedure in the manual, but I think if you drained the two filters on the block first, left the drain valves open so it can draw air, then drained the primary, it wouldn't be able to siphon from the tank.
If you collect the drained fuel into clean containers, you can let it set for awhile so any water and junk settles to the bottom, then pour the clean fuel off the top back into the tank so not much is wasted.

I'll try draining the secondaries first and leaving the petcocks open. Thanks for the advice.

 

[GunInstructordotcom]

I'll try draining the secondaries first and leaving the petcocks open. Thanks for the advice.

OK, so I changed the secondary fuel filters. The old o-ring gaskets were tough to get out. I suspect the mechanic who last replaced the filters just reused the old gaskets. They were hard and brittle and took about an hour or more for my wife and I taking turns to get them out with the help pf a dental tool. I used the thinner set of new gaskets that came with the NAPA filters. The thicker set does not fit. I had to stretch them out a bit to get them to fit in the grooves. Installed the filters and housings. I just switched the ignition on and when the pressure filled the filters, they both leak a bunch. Is there another set of gaskets I can obtain that will work?

 

[NY Tom]

I’m not sure if it’s the best idea or not but on mine I ended up putting orings in each injection line connection to fix the same problem your having. My hydraulic head was old and pitted and that’s the only way I could keep it from leaking.

I have a leak at one injection line only. Tried a lot of things to fix it to no avail. I would like to know more about your fix and how you did it.

 

[Jeepsinker]

This may help.

Multifuel injector pump videos

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[Jeepsinker]

Oh, here's another.

M35A2 fuel system

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.

www.youtube.com

 

[NY Tom]

Thanks Jeepsinker all good information there in those links.

It's to the point now where I think I have to pull the head just to try and fix where the #3 injection line goes in. Tried new lines, new crush ferrules. Tried lapping the tapered part inside the head. O-Ring idea sounds like it might be what I need.

Not sure what else to try. This is a very annoying leak that doesn't show up at an idle. Only when you are running on the road.

Hate to buy a whole head for a leak on one line only.